Are Metering & Focus Tied? #121

Are Metering & Focus Tied? #121

Although it seems obvious that there is a difference between focus and metering, there still seems to be a lot of confusion about how they are related. Let's dive in. First, focus is about you or your camera moving the glass elements in your lens so that your image is sharp or blurry. While metering is the system inside your camera that measures how much light is bouncing back from your scene and tells your camera what the appropriate setting should be to achieve a good middle ground exposure. And most cameras allow you to dictate the area of the frame that it is measuring. It also allows you to dictate the area that it will focus on as well. But you have to start thinking of metering and focus as two separate systems. So where's the confusion? The confusion happens when people think that the two are tethered. The fact is, it can be, but that's not normal. I think the confusion may be caused by the fact that this is how most smartphone cameras operate. With a smartphone, when you touch your screen, it both focuses and meters where you touch the screen. You'll notice that when you touch the screen on a bright area, the entire frame will become darker. And if you touch a dark area, the entire scene will become lighter. For the most part, this is not what's happening in a DSLR or even a mirrorless camera. Let's start with the DSLR. To be clear, DSLR is heading towards extinction. But they are still out there, so let's talk about that first. Pretty much over 90% of DSLR cameras are incapable of metering off of a focus point, unless you are in live view. In which case, it may be able to do that. Within the Canon lineup of DSLRs, only their top-of-the-line camera, that's one camera, can tether the metering to the focus point. Having said this, when you're using spot metering, that's the metering system that only measures 1-4% of the very center of the frame, and you have your camera on spot focus and put that focus point in the center, then you have de facto a metering system that is metering where the focus is. But if you move the focus point away from the center, you will see that the metering is not following the focus point. To see this in action, set your camera to spot metering and single point focus, and put the focus in the center. Point the center of your camera to some trees. Take a photo. Without moving the camera, move the focus point to the clouds above, and you'll see that the image exposure remains the same. As you can see, the meter is not chasing the focus point. If you are using your live view, that is, if you're shooting from your LCD and not your viewfinder, very often your camera will likely, but not always, focus and take a meter reading where you place your focus point or touch the screen, for those with the touch screen. So what about mirrorless cameras? I would have thought that with all mirrorless cameras that you would be able to tether spot focus and spot metering. But guess what? You can't. It depends on the camera. At this point, neither Nikons nor Canons can do this. But the Sony can. Although Sony allows you to tether spot metering and spot focus, it will not do this if you're using focus tracking. Your spot focus needs to be static. Unfortunately, you will need to go through your manual for instructions on how to set this up and whether or not you even have this capability.

Then there's the question, why would you want to do this? And are there workarounds if you don't have this capability? Why wouldn't you put your camera in matrix or evaluative metering where the camera takes the entire frame into account. Well, for my kind of shooting, yes, that's exactly what I do. But I don't generally shoot small objects or animals where this is most beneficial. For example, let's say you're photographing a bird in the sky. In this situation, the bird is usually less than a third of the entire frame and likely to be dark toned. If you're using matrix metering, where the camera is measuring almost the entire frame, then the bright sky will overwhelm the exposure and will leave your bird extremely dark. But if you have the ability to spot meter on your focus area, then you would mostly resolve this problem, because then the meter reading will only be based on where the focus area is. Of course, if your bird is either very dark or very light, you will still need to make some adjustments against that, but you are going to get much closer to the exposure you need.

So what's the workaround if your camera can't do this? Apparently, in most canons and Nikons, the camera will more heavily weight the metering on the active focus area by about 1-2 stops when you're using Matrix or Wide Area Metering. It's not a perfect system, but this will most certainly get you closer to the right exposure. For a better understanding of metering, please check out episode 59. For a better understanding of focus, check out the last episode. I hope that was helpful. And if you have a question you want answered on this pod, please send an email to zim@ nycphotosafari.com.